THERE IS A BIT of controversy regarding the use of BMI or body mass index. BMI is a measure of body fat but the metric should be used in conjunction with other measures of health risk, such as a patient’s genetics, blood pressure, cholesterol and other metabolic factors, according to the American Medical Association (AMA).
BMI, which roughly estimates a person’s body fat based on their weight and height, doesn’t distinguish between body fat and lean body mass. BMI also doesn’t capture where on the body people carry excess fat. This is important because upper body fat increases the risk of type 2 diabetes and coronary artery disease more than does lower body fat.
Besides, BMI is “inaccurate in measuring body fat in multiple groups” because it doesn’t account for differences in the relative body shape and composition of people of different sexes, ages, races and ethnicities.
This is partly because the BMI scale is based on the imagined ideal Caucasian. Crucially, this means that the same BMI thresholds don’t indicate the same level of disease risk in all patients. In general, the widespread use of BMI in medical research skews scientists’ and doctors’ understanding of the risk of disease and death linked to obesity.
Frequently, in studies that find a correlation between high BMI and disease or death, the researchers fail to account for other key factors that may affect people’s risk, like a history of smoking, alcohol use, medication use or a family history of disease. In addition, such studies often don’t account for the expected fluctuation of weight with age and lack nuance regarding the amount of time participants spend in a given BMI category, and therefore don’t capture how those factors shape later disease risk.
Based on the new report, the AMA has adopted a new policy on the use of BMI. The association now recommends that, due to the limitations of the metric, BMI should be used in conjunction with other valid measures of risk, including but not limited to measures of visceral fat (the fat that surrounds the internal organs), relative fat mass (a body fat estimate that uses a height-to-waist ratio) and waist circumference. Genetic factors, including family history of diabetes and heart disease, and metabolic factors, such as high blood pressure and fasting blood sugar levels, are additional metrics to consider.
And the AMA emphasized that overreliance on BMI can lead to the underdiagnosis and undertreatment of eating disorders because doctors may not flag affected patients with “normal” or “above normal” BMIs. Insurance companies also use BMI to determine whether people’s inpatient eating-disorder treatments will be covered, and this can lead to substandard treatment for patients who don’t meet the weight cutoffs, the AMA noted. There are numerous concerns with the way BMI has been used to measure body fat and diagnose obesity, yet some physicians find it to be a helpful measure in certain cases. It is important for physicians to understand the benefits and limitations of using BMI in clinical settings to determine the best care for their patients. By Manny Palomar, PhD (EV Mail Feb. 5-11, 2024 issue)
